HARBOUR CONSTRUCTION

IN a previous article (Vol. I., p. 370 foil.) has been described the extremely arduous work of the lighthouse engineer and the nature of the terrific destructive forces with which he has to contend. Another branch of marine engineering, that of harbour construction, is beset with the same difficulties, though possibly in not so aggravated a form, as harbour works are not so isolated as the rocks on which lighthouses have to be raised.

We are concerned here primarily with works carried out to oppose the violence of the waves, and to render safe for shipping areas of water which, but for some such protection, would be utterly unsuitable for anchorage in bad weather. The breakwater is a mere barrier, cither reducing the size of a wave or checking its progress altogether. Its shape and character depend partly on the conditions of the site, partly on the work for which it is designed. It may be either an artificial bank of rubble with long slopes paved on the top ; or a rubble mound brought up to within a few feet of low-water level at spring tides, and capped with a built pier; or a more or less vertical wall based upon the sea bottom. The breakwaters of Plymouth, Portland, and Dover Harbours respectively are good examples of the three ty;n«s. Wo may add that different forms of construction are found in some cases in one breakwater at different depths of water. Thus, what begins at the